Differential amplifier

Differential Amplifier

A differential amplifier is a type of electronic amplifier that amplifies the difference between two input signals while rejecting any common-mode signals. It is commonly used in various applications, such as in audio amplifiers, operational amplifiers, and communication systems.

Operation

The basic operation of a differential amplifier relies on the use of two input signals, commonly referred to as the non-inverting and inverting inputs. The amplifier amplifies the voltage difference between these two inputs, while suppressing any voltage that is common to both inputs.

The differential amplifier consists of two transistors, typically bipolar junction transistors (BJTs) or field-effect transistors (FETs), connected in a configuration that allows for differential amplification. The non-inverting input is connected to the base (for BJTs) or gate (for FETs) of one transistor, while the inverting input is connected to the base or gate of the other transistor. The emitters (for BJTs) or sources (for FETs) of both transistors are commonly connected together, forming a common emitter or common source configuration.

Applications

Differential amplifiers find extensive use in various applications due to their ability to amplify the difference between two input signals. Some common applications include:

1. Operational Amplifiers: Differential amplifiers are a fundamental building block of operational amplifiers (op-amps). Op-amps are widely used in electronic circuits for tasks such as amplification, filtering, and signal conditioning.

2. Audio Amplifiers: Differential amplifiers are used in audio amplifiers to amplify the difference between the left and right audio channels, providing stereo sound reproduction.

3. Communication Systems: Differential amplifiers are used in communication systems, such as in radio frequency (RF) receivers and transmitters, to amplify and process weak signals while rejecting noise and interference.

4. Instrumentation Amplifiers: Differential amplifiers are used in instrumentation amplifiers, which are specialized amplifiers designed for accurate measurement of small signals in the presence of noise.

Advantages

Differential amplifiers offer several advantages over single-ended amplifiers:

1. Common-Mode Rejection: By amplifying only the difference between two input signals, differential amplifiers reject any common-mode signals that are present on both inputs. This helps in reducing noise and interference.

2. Increased Linearity: Differential amplifiers provide improved linearity compared to single-ended amplifiers, resulting in more accurate amplification of signals.

3. Higher Gain: Differential amplifiers can achieve higher gain compared to single-ended amplifiers, making them suitable for applications that require amplification of weak signals.

Conclusion

In conclusion, the differential amplifier is a versatile electronic amplifier that amplifies the difference between two input signals while rejecting any common-mode signals. It finds widespread use in various applications, including operational amplifiers, audio amplifiers, communication systems, and instrumentation amplifiers. With its advantages of common-mode rejection, increased linearity, and higher gain, the differential amplifier plays a crucial role in modern electronic systems.